Chlorination of ores with catalyzed metal chlorides

ABSTRACT

The invention comprises a process for the manufacture of metal chlorides by the double-decomposition reaction between a metal chlorinating agent and a metal oxide having greater affinity for chlorine than does the oxide of the metal chloride, and in the presence of small amounts of boron chloride or functionally equivalent boron compounds that increase the rate and degree of completion of the reaction. 
     A major application of this invention is for the making by the chlorination of clay of aluminum chloride and alumina intermediates for the manufacture of aluminum metal. 
     SiCl 4  is formed in the carbo-chlorination of clay or other aluminous-siliceous ores. The SiCl 4  by this invention is catalyzed with BCl 3  and reacted with calcined clay to produce AlCl 3  and SiO 2 . The practical use of SiCl 4  to make AlCl 3  thus eliminates the previous costly burden of waste SiCl 4  production.

BACKGROUND OF THE INVENTION

Carbo-chlorination has been utilized for the extraction from ores ofmetal values like aluminum, titanium and zirconium as volatilechlorides. Many otherwise useful ores have an excessive silica contentwhich also carbo-chlorinates to form silicon tetrachloride and in theprocess consumes costly carbon, increases the volume of gases hence sizeand cost of plant equipment; has required costly refrigeration energyfor its collection due to its high volatility (60° C.b.p.); and therecovery of its chlorine content is mandatory and that could beaccomplished heretofore only by oxidation which consumes high-energyoxygen while posing difficult equipment problems at the 900°-1000° C.temperature of oxidation in the presence of chlorine an oxygen.Furthermore, the silica formed by the oxidation is very fine, hard tocollect from the corrosive chlorine gases and poses a disposal problemdue to its 5-10 lbs. per cubic foot bulk density.

Therefore, high silica ores have not been carbo-chlorinated on a largecommercial scale due largely to the high costs and problems due to theSiCl₄ co-production.

The instant invention by reacting the SiCl₄ with metal oxides at apractical speed and degree, economically makes useful metal chloridesfrom the previously detrimental SiCl₄.

The instant invention therefore economically and uniquely utilizes SiCl₄thus opening the way for the beneficiation by chlorination of manysilica-containing ores. The valuable metals as oxides in the ore areconverted ordinarily to metal chloride vapors by this invention andthen, with or without purification, are sold as such or converted totheir respective valuable oxides or metals.

A most urgent need for the instant invention is in the manufacture ofaluminum metal. There are two methods now used to make that metal. Thefirst method is the old Hall electrolytic process in which pure aluminumoxide is dissolved in molten cryolite and then electrolyzed to make themetal. The second method is the new Alcoa smelting process to whichalumina is chlorinated to make aluminum chloride which is then mixedwith conductive metal chlorides and electrolyzed to make aluminum metaland chlorine, the latter is being recycled.

The alumina used for commercial aluminum production by either of theabove processes has been made exclusively by the old Bayer process whichuses only high grade bauxites, the supply of which is limited and occursin only a relatively few countries. On the other hand, there is alimitless and widespread supply of clay over the face of the earth butthere have been no commercial plants built and only one patent issuedfor making pure metallurgical grade alumina or AlCl₃ bycarbo-chlorination of clay. The co-chlorination of silica with thealumina in clay obviously has been a major drawback to clay use.

The assignee of the instant invention has been active in developingimprovements in the chlorination of aluminous ores, such as U.S. Pat.No. 4,083,923 which describes a complete process of making metallurgicalgrade alumina by carbo-chlorination of kaolinitic clay and which hasbeen issued as the first such complete proces patent; U.S. Pat. No.4,082,833, which covers the use of sulfur catalyst to improve claychlorination rates and yields. However, these processes carbo-chlorinatethe silica as well as the alumina in the clay with the usual economicand energy penalty.

In view of the aforementioned detriments associated with chlorination ofsilica, there naturally has been some research directed to suppressingthe chlorination of silica in clay. For instance, U.S. Pat. No.1,866,731 to Staib and British Pat. No. 305,578 teach that the recyclingof silicon tetrachloride along with chlorine fed to the clay in thecarbo-chlorinator gives virtual elimination of net SiCl₄ production.However, Staib does not teach the use of BCl₃ as a catalyst to increasethe reactivity of SiCl₄. Also Staib uses a large excess of SiCl₄ torepress further SiCl₄ formation, reportedly by the law of mass action,and, furthermore, the chlorinating agent is elemental chlorine withcarbon as a reductant. In the instant invention, on the other hand, thechlorinating agent is the metal chloride SiCl₄ activated by smallamounts of BCl₃ without any form of reductant. Also, this prior artprocess apparently never has been used commercially presumably becauseof inoperability indicated by actual laboratory tests.

Other references cited below involve the reduction in the chlorinationof silica in clay carbo-chlorination by means of catalysts. But hereagain, the carbo-chlorination reaction is used with elemental chlorineas the chlorinating agent and with reductant necessary. Applicants, onthe other hand, use a different double-decomposition reaction (not acarbo-chlorination) in which metal chloride, SiCl₄, is the chlorinatingagent and reductant is not used.

None of the following prior art references shows or suggests applicant'suse of BCl₃ as a catalyst for SiCl₄ in a separate double displacementreaction with clay or metal oxides.

Reference cited are:

Arne Landsberg, Metal. Trans. B, Vol. 8B, Sept., 1977 page 435-441. NaClis used as a catalyst to reduce chlorination of SiO₂ incarbo-chlorination of clay. Significantly, Landsberg also contactedSiCl₄ with calcined clay with and without NaCl. He observed only FeCl₃evolved and found the treated clay to react much more slowly insubsequent carbo-chlorination.

Russian references Ya. E. Seferovich, J. Chem Ind. (Moscow) No. 10(1934) 62-4 and E. I. Krech, J. of General Chemistry (USSR) 7 Paper #8,pp 1249-63 (1937) mention means to preferentially chlorinate aluminaover silica in clay but by the use of catalysts (Na₂ B₄ O₇, NaCl) in thecarbo-chlorination reaction.

Assignee's allowed U.S. Application Ser. No. 814,834 and U.S. Pat. No.4,083,927 also cover catalysts for silica suppression duringcarbo-chlorination, namely, alkali metal oxyanions and boron compounds,respectively.

However, all carbo-chlorinations with or without silica-suppressingcatalysts produce considerable amounts of SiCl₄, usually representing15-95% of the silica in the clay, so the instant invention would applyto recover values from the SiCl₄ in the gaseous products of thosecarbo-chlorinations.

Of course, it has been well known that SiCl₄ reacts as a chlorinatingagent with metal oxides according to the oxide-chlorine affinity series.

Nowak, U.S. Pat. No. 3,244,509 discloses the use of SiCl₄ to purify oreof Fe₂ O₃ by converting Fe₂ O₃ to FeCl₃ and another Nowak U.S. Pat. No.3,466,169 shows the SiCl₄ reaction with alumina. However, neither ofthese reference refers to BCl₃ catalyst with the SiCl₄ to react withclay or other oxides.

In summary there are no references in the prior art that showimprovement, by the use of BCl₃ catalyst, in the rate and degree of thedouble decomposition reaction between a metal oxide and a metal chloridechlorinating agent like SiCl₄.

SUMMARY OF THE INVENTION

The invention comprises the double-decomposition reaction between ametal chloride chlorinating agent and a metal oxide having greateraffinity for chlorine than does the oxide of the metal chloride agentand in the presence of small amounts of boron chloride or functionallyequivalent boron compounds that increases the rate and degree ofcompletion of the reaction. The double decomposition chlorinationreaction is illustrated by this equation:

    YO.sub.2 +ZCl.sub.4 →YCl.sub.4 +ZO.sub.2

The reaction proceeds because YO₂ has a greater affinity for chlorinethan does ZO₂ ; or YO₂ is higher in the metal oxide-chlorine affinityseries than ZO₂. The rank in the series is established by thermodynamiccalculations.

The preferred application of the invention is for the production ofvirtually only AlCl₃ instead of AlCl₃ and SiCl₄ in the chlorination ofclay. The clay is conventionally carbo-chlorinated to AlCl₃ with evengreater amounts of SiCl₄ as the serious economic detriment previouslydescribed. By the proces of the instant invention, that silicon chloridecatalyzed with BCl₃ is effectively reacted principally with the aluminacomponent of fresh calcined clay so that substantially only AlCl₃ (withsmall amounts of TiCl₄ and FeCl₃) is the net product rather than SiCl₄and AlCl₃. Offgases from the clay carbo-chlorination containing SiCl₄can be directly reacted with calcined clay in the presence of BCl₃catalyst or the SiCl₄ can be separated in whole or part from the gasstream and then reacted with clay in the manner of this invention.

It is obvious that this invention will apply also to catalyze othermetal chlorides than SiCl₄ to make them more active chlorinating agentsfor metal oxides. TiCl₄ for instance, is similar to SiCl₄ in propertiesand would be similarly catalyzed by BCl₃.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The present invention broadly comprises the chlorination of a metaloxide by a metal chloride chlorinating agent in the presence of borontrichloride to produce a metal chloride from the original oxide; and anoxide from the original metal chloride. The boron trichloride can bemixed as such with the chlorinating agent or introduced as functionallyequivalent boron-containing compounds.

The preferred embodiment is the reaction of calcined kaolin clay withsilicon tetrachloride as given by the following double-decompositionequation for the major alumina component of the clay.

    2 (Al.sub.2 O.sub.3.2SiO.sub.2)+3SiCl.sub.4 =4AlCl.sub.3 +7 SiO.sub.2

It has been found that the above chlorination is very slow andincomplete even at the maximum permissible reaction temperature of 1000°C. (clay forms refractory compounds at higher temperatures). The rateand degree of reaction are greatly enhanced by the addition to thereaction of small amounts of boron trichloride and/or functionallyequivalent boron-containing compounds.

The mechanism by which boron compounds act as catalysts or reactionpromoters in the above chlorination reactions has not been fullyestablished, but it seems from tests that any boron compound that willform boron trichloride in the reaction zone will qualify as catalyst orpromoter. Boron compounds that will chemically combine with silicontetrachloride to yield boron trichloride would be reaction promoters orcatalysts.

The following boron compounds would be effective as they would form BCl₃with SiCl₄ in the chlorinator: boron oxide, boric acid, sodium borate,aluminum borate, or the like. Boron trichloride is usually preferred asit is readily purchased or produced for makeup and it is recycled in thesystem so its use would avoid making changes in composition of the boroncatalyst.

BCl₃ is a vigorous chlorinating agent for most oxides like those inclay:

    Al.sub.2 O.sub.3 +2BCl.sub.3 =2AlCl.sub.3 +B.sub.2 O.sub.3 Equation 1

    3TiO.sub.2 +4BCl.sub.3 =3TiCl.sub.4 +2B.sub.2 O.sub.3      Equation 2

    Fe.sub.2 O.sub.3 +2BCl.sub.3 =2FeCl.sub.3 +B.sub.2 O.sub.3 Equation 3

    2B.sub.2 O.sub.3 +3SiCl.sub.4 =4BCl.sub.3 +3SiO.sub.2      Equation 4

According to one proposed theory, the reaction promotion by BCl₃ couldbe caused by fast initial reactions with the metal oxides as shown inequations (1), (2), (3) to release the respective metal chlorides andmake B₂ O₃ which in turn would react with SiCl₄ (equation (4)) toregenerate BCl₃ and deposit SiO₂. Since B₂ O₃ is a fluxing andcomplexing agent, it could well promote ion mobility and reactivity atthe reaction interfaces. On the other hand, the BCl₃ might complex withthe SiCl₄ then dissociate in the reaction zones to provide some freeradicals that react more rapidly. This invention is not to be limited byany of the aforelisted explanations.

By-products FeCl₃, TiCl₄ and some trace metal chlorides also areproduced by reaction of the SiCl₄ with their respective oxides. Thetitanium tetrachloride is a readily salable, valuable high tonnage itemwhile the iron chloride can be sold as such for sewage treatment oroxidized to make pigments or feed for making pure iron metal.

Some types of ores that could be carbo-chlorinated to make some SiCl₄that would be advantageously utilized by the practice of this inventionare:

Aluminum silicates like kaolinitic clays, haloysite, feldspars, ballclays, fire clays, coal shales and slates; nepheline syenites; fly andother ashes from combustion of fuel; aluminum oxides as siliceousbauxites, laterites, and aluminous and other ores containing silica orsiliceous minerals.

Also, other applicable ores would comprise those valuable with metals asoxides along with silica or siliceous compounds, said metal oxides beingcarbo-chlorinateable.

The SiCl₄ would react with the following ores or oxides, as examples, tomake silica and more valuable metal chlorides.

Most preferred are calcined kaolinitic clay and other aluminum silicatesreactive with catalyzed SiCl₄. Others: reactive transition aluminas likeamorphous, gamma, eta or chi phases; and ores containing oxides,silicates or other compounds of the following metals and reactive withcatalyzed SiCl₄ : Mo, Al, Cr, Zr, Ti, Fe, Mg, Sn, As, Co, Ni, Sb, Zn,Mn, Bi, Cd, Cu, Pb, Hg.

Furthermore, the chloride of any of the metals listed in the tablefollowing can chlorinate the metal in any of the oxides listed later inthe table. The list shows the relative chlorine affinity of metaloxides. Accordingly, the instant invention includes any chlorination ofa metal oxide in which the metal chloride chlorinating agent iscatalyzed by BCl₃ or functionally equivalent boron compounds to increasechlorination rates or yields. For instance, TiCl₄ would react morerapidly and completely with any of the oxides following it in the listin the presence of BCl₃.

The double decomposition chlorination reaction of the present inventionis exemplified with BCl₃ catalyzed SiCl₄ as the chlorinating agent withcalcined kaolinitic clay in the following working examples wherein allparts and percentages are by weight unless otherwise specified.

EXAMPLE 1

A readily available Georgia kaolinitic clay containing on a dry basis,38% Al₂ O₃, 44% SiO₂ ; 1.5% Fe₂ O₃ ; 2.5% TiO₂ and 14% H₂ O, was firstdried at 140° C. to remove free moisture and thereafter was ground toabout -200 mesh (Tyler series). A charge of about 23 gms of the dry claywas calcined in a 40 mm diameter batch fluid bed reactor at 900° C. for20 mins. under a purge of 400 cc/min argon to remove all free andchemically bound water. After 20 mins., the argon gas was directedthrough a flask containing liquid SiCl₄ then into the reactor. SiCl₄ wasthus vaporized into the argon stream at a rate of 0.265 gms SiCl₄ permin. for 60 min. After the stated reaction time, the reaction mass wascooled, weighed and analyzed for residual metals from which theconversion of metal oxides was calculated.

Examples 2, and 3 employed exactly the same clay, apparatus andconditions for calcination as in Example 1. In chlorination there weresmall differences in the rates of SiCl₄ evaporated into the argon. Thebig difference between Example 1 versus Examples 2 and 3 was theintroduction in Examples 2 and 3 of BCl₃ gas into argon gas stream inaddition to the SiCl₄. Example 3 employed much more BCl₃ gas thanExample 2. Conditions were virtually identical in all other respects.

Results were tabulated in Table I.

                                      TABLE I                                     __________________________________________________________________________    DATA ON TEST CONDITIONS AND CONVERSIONS                                       A    B   C    D    E   F  G    H   I   J   K   L   M                                                         INCREASE IN CONVERSION                                                        FROM BCl.sub.3                                 Argon    SiCl.sub.4                                                                         BCl.sub.3        Al.sub.2 O.sub.3                                                                      TiO.sub.2                                                                             Fe.sub.2 O.sub.3               flow-    feed feed             Dif.    Dif.    Dif.                           rates    rate rate % CONVERSION                                                                              in      in      in                             Example                                                                            cc/min                                                                            gms/min                                                                            gms/min                                                                            Al.sub.2 O.sub.3                                                                  TiO.sub.2                                                                        Fe.sub.2 O.sub.3                                                                   Conv.                                                                             Ratio                                                                             Conv.                                                                             Ratio                                                                             Conv.                                                                             Ratio                      __________________________________________________________________________    1    400 0.265                                                                              0     6.1                                                                               10.0                                                                             91.1                                                                              --  --  --  --  --  --                         2    400 0.273                                                                              0.0183                                                                             39.0                                                                              100.0                                                                            100.0                                                                              32.9                                                                              6.4 90.0                                                                              10.0                                                                              8.9 1.1                        3    400 0.290                                                                              0.0915                                                                             44.0                                                                              100.0                                                                            100.0                                                                              37.9                                                                              7.2 90.0                                                                              10.0                                                                              8.9 1.1                        __________________________________________________________________________

Example of calculations:

(H-2)=(E-2)-(E-1)=39-6.1=32.9%

(I-2)=(E-2)/(E-1)=39.0/6.1=6.4

Other columns are similarly calculated.

Table II provides certain compositions and ratios calculated from thedata in Table I in order to establish the effect of variables and theapplicable limits of reagents and catalysts.

                                      TABLE II                                    __________________________________________________________________________    CONCENTRATION AND RATIOS OF REAGENTS AND CATALYST.                            A    B   C    D   E    F    G    H    I                                                                             SiCl.sub.4 fed,                                       Gas Composition                                                                        BCl.sub.3 to                                                                       BCl.sub.3 to                                                                       SiCl.sub.4 to                                                                      % stoich.                                             %   %    SiCl.sub.4                                                                         dry clay                                                                           dry clay                                                                           on Al.sub.2 O.sub.3                     Example       by  by   weight                                                                             weight                                                                             weight                                                                             in dry                                  No.  Item                                                                              ccs/min                                                                            volume                                                                            weight                                                                             ratio                                                                              ratio                                                                              ratio                                                                              clay                                    __________________________________________________________________________    2    Argon                                                                             400  91.0                                                                              71.0                                                             SiCl.sub.4                                                                        36.0 8.2 27.2           .71  75.0%                                        BCl.sub.3                                                                         3.5  0.8 1.8  .067 .048                                                   Total                                                                             439.5                                                                              100.0                                                                             100.0                                                       3    Argon                                                                             400  87.8                                                                              65.2                                                             SiCl.sub.4                                                                        38.2 8.4 26.5           .76                                               BCl.sub.3                                                                         17.5 3.8 8.3  .316 .239      79.6%                                        Total                                                                             455.7                                                                              100.0                                                                             100.0                                                       __________________________________________________________________________

Certain observations from the above tables are significant.

TiO₂ --The effectiveness of this invention for the chlorination of TiO₂is apparent; it chlorinated 10 times faster when BCl₃ catalyst was used.

Fe₂ O₃ --The relatively little effect of BCl₃ catalyst on chlorinationof Fe₂ O₃ can be attributed to the fact that the form of iron as foundin clay is so quickly chlorinated without a catalyst that the effect ofa catalyst would be small. However, other forms of Fe₂ O₃ and most metaloxides above SiO₂ in the chlorine affinity series would chlorinate moreslowly so the catalyst would play an important part in improving thereaction rate and degree.

1. BCl₃ concentration.

Even with the BCl₃ at only 0.9% by volume (1.9% by weight) in the feedgas stream, its effect was to increase the reaction rates or yields withAl₂ O₃ and TiO₂ about 6-10 times. Considerably less BCl₃ obviously wouldbe quite effective because about a five-fold increase in itsconcentration (Example 3 vs. 2) caused only a relatively small increasein the reaction rates and yields. The profound effect of only afractional volumetric percentage of BCl₃ was indeed unexpected, andestablished the unique catalytic effect of BCl₃. The BCl₃ is effectivein practical concentrations from about 0.2% to 12% by weight of the feedgas stream depending on the concentration of the SiCl₄ and otherconditions during the reaction. The preferred range is about 0.5%-7% byweight of the gas stream.

2. The weight ratio of BCl₃ to SiCl₄ varied from 0.067 to 0.316; theformer was effective and the latter appeared in excess. At the lowerend, a BCl₃ /SiCl₄ ratio of about 0.01 would be effective especiallywith higher concentrations of SiCl₄. At the high end, a BCl₃ /SiCl₄ratio of 0.40 would be practical. The higher ratios would be especiallyuseful with low concentrations of SiCl₄ to maintain an adequateconcentration of BCl₃ in the total stream.

Accordingly, the range of BCl₃ /SiCl₄ would be 0.01-0.40 with thepreferred range of 0.03-0.20.

3. SiCl₄ Concentration

SiCl₄ concentration in the feed gas stream was only 8.2% by volume,amazingly reactive when catalyzed, as there was relatively poor contactwith the clay due to the low concentration. In commercial practice, theconcentration of the SiCl₄ could be considerably increased if necessary.The SiCl₄ concentration can be varied from about 10% to about 100% byweight of feed gas under the scope of this invention.

4. The ratio of BCl₃ to dry clay varied from 0.048 to 0.239, with usablerange of about 0.01 to about 0.4, preferred range of about 0.03 to about0.2.

5. Stoichiometry of SiCl₄ to Al₂ O₃ in clay.

It is significant that the weight ratio of SiCl₄ to Al₂ O₃ in dry claywas about 1.9 or about 76% of stoichiometric for conversion of all theAl₂ O₃ in the dry clay charge, so, considering the demand for SiCl₄ forreaction with the TiO₂ and Fe₂ O₃, there was not enough SiCl₄ fed tocompletely convert the Al₂ O₃. The significance of these comments isthat better conversion of both SiCl₄ and of Al₂ O₃ in clay could beexpected commercially as by use of countercurrent reactors and bettercontact of the SiCl₄ with the clay.

Demonstation of Two-stage Chlorination Process

The examples below demonstrate the effect of BCl₃ catalyst in the secondstage of a 2-stage chlorination process. In the first stage, theconditioned clay was carbo-chlorinated to produce offgases containingprimarily AlCl₃, SiCl₄ and carbon oxides which were then passed througha second stage containing conditioned clay. The SiCl₄ reacted with theAl₂ O₃ in the clay to make AlCl₃ and SiO₂. The effect of BCl₃ on thereaction of SiCl₄ in the second stage is obvious.

EXAMPLES 4, 5 and 6

A series of two stage chlorination experiments were carried out to showthe effect of the double displacement reaction with and without BCl₃catalysts in the second stage and also to establish desirableconcentrations of BCl₃ catalyst. The first step comprisedcarbo-chlorination of clay using sulfur as the catalyst, and in thesecond step the hot offgases from the first reactor were passed into asecond reactor containing 200 mesh calcined clay and into which BCl₃ gascatalyst was introduced to mix with the hot gases.

Description of the Tests

Two 40 MM ID vertical fused quartz tubes each fitted with a mediumquartz fritted disc were connected together with a 40 MM Pyrex tube(transition tube) to which a tube was connected for introduction of theBCl₃ gas catalyst. A tube connected the first reactor to supplies ofnitrogen, chlorine, H₂ S, or BCl₃ gases.

Shell heaters were placed around the quartz reactors and a heater tapewas wrapped around the transition tube. The two reactors were heated to900° C. and the temperature controlled by means of a thermocouple and adigital readout potentiometric controller 31 gms of a mix containingcalcined clay and approximately 35% lignite char was added to the firstreactor under a stream of 250 ccs/min N₂. The transition tube wasconnected to the first and second reactors and heated to 300° C. Intothe second reactor 30 gms of calcined clay was added. A cold condenserand a scrub containing caustic soda solution were connected to thesecond reactor. When both reactor temperatures had lined out at 900° C.the nitrogen purge was removed and chlorine at 100 ccs/min and H₂ Scatalyst at 5 ccs/min were introduced into the first reactor and at thesame time BCl₃ at stated controlled rate was introduced into thetransition tube to the second reactor in Example 5 as shown in thefollowing Table 3. For Example 6 of that Table, the BCl₃ was introducedalong with chlorine and H₂ S into the first reactor. The experiment wasallowed to proceed for approximately 2 hours and the Cl₂, H₂ S and BCl₃flows were stopped. N₂ was introduced, and the reactors allowed to cool.After cooling, the apparatus was disassembled and the residues,condenser and scrub were measured and analyzed. The results of theexperiments are shown in the following Table 3.

                                      TABLE 3                                     __________________________________________________________________________                                       GAS COMPOSITION                            1st REACTOR           2nd REACTOR Entering 2nd Reactor                        EXAMPLE        CATALYST    CATALYST                                                                             % SiCl.sub.4                                                                       % BCl.sub.3                                                                        % SiCl.sub.4                      #      MIX     ADDED  SOLID                                                                              ADDED  By Weight Utilized in Second                __________________________________________________________________________                                                Reactor                           4      Clay + Carbon                                                                         H.sub.2 S                                                                            Clay 0      12   0    17                                       + Chlorine                                                             5      Clay + Carbon                                                                         H.sub.2 S                                                                            Clay BCl.sub.3                                                                            18   2    53                                       + Chlorine                                                             6      Clay + Carbon                                                                         H.sub.2 S                                                                            Clay --     14   0.9  59                                       + Chlorine                                                                            + BCl.sub.3                                                    __________________________________________________________________________     The above tests showed the powerful effect of BCl.sub.3 in the second ste     and that a BCl.sub.3 concentration as low as 0.9% of the gas stream was a     effective as 2%.                                                         

The effect of other variables is discussed below.

Particle Size

The particle size used in the above tests was -200 mesh, obtainablereadily in hammer, impact, ball and other types of mills, but otherparticle sizes might be desirable for different types of apparatus. Thesmallest practical particle size should be used to expedite the reactionrate.

Calcination

In the best practice of this invention, the clay must be properlycalcined to make it adequately reactive with the catalyzed SiCl₄. Theconditions for calcination of clay for this invention are in atemperature range of 600°-950° C., preferably 790°-950° C. and flashcalcined (sudden exposure to the operating temperature to cause the claystacks to open up for better diffusion of gas). This practice alsoreduces the time of exposure of the clay so would tend to avoid thereduction of clay activity due to overheating above about 975° C. Theclay should be calcined, preferably to reduce the loss on ignition fromcombined water, to below 0.5%, preferably to 0, to avoid formation ofHCl.

Gas reducing conditions in calcination are usually beneficial. Someconditions for calcining clay have been set forth in the examples butpatent application Ser. No. 814,834 and U.S. Pat. No. 4,083,927 describemethods for calcining clay under conditions and/or in the presence ofadditives (sulfur, borates, alkali metal oxyanions, and flash reducingcalcination) to make the clay more reactive. The instant inventionincludes the use of such more reactive calcined clays for the reactionwith catalyzed SiCl₄.

Form of and Incorporaton of Catalyst

As previously mentioned, the boron catalyst can be added not only asBCl₃ to the SiCl₄ gas stream or reactor, but also as previouslyindicated functionally equivalent boron compounds added to the claybefore or after calcination with or without grinding together or use ofother bonding means such as binders, balling, briquetting, pressing,etc. The clay or clay-catalyst mix could be comminuted as desired aftercalcination.

Pressure

The process can be operated well under atmospheric pressure or underhigher pressure, to reduce size and cost of equipment. The process canbe carried out, for instance, at an absolute pressure of about 10 toabout 200 pounds per square inch.

Temperature

The process is applicable to the chlorination of a large number of metaloxides with their corresponding chlorides having a wide range of boilingpoints; for instance: metal chlorides made from oxides of metals listedon the bottom of page 6 have boiling points ranging from 110° to 1000°C. The amount of metal chloride vaporized would be determined by thevapor pressure at the temperature of chlorination and the amount andcomposition of gases passing through the chlorinator.

However, the activation energy for most of these reactions demands atemperature of at least about 500° C. Hence, the broad temperature rangeis about 500°-1000° C. For the reaction of catalyzed SiCl₄ and calcinedclay, the range would be 800°-1000° C. with a preferred range of about850°-950° C.

Apparatus

To accomplish the best operation of this process, there are fortunatelymany types of commercial apparatus available, such as shaft furnaces;fluid, static and fast bed reactors; rotary kilns; solid-gas contactors,rabbled hearth furnaces and the like, and which can be operatedbatchwise, continuously or semi-continuously, countercurrently orconcurrently. There are commercially available construction materials tocontain the reaction that will last and not contaminate the products.

This invention applies not only to the catalysis with BCl₃ of SiCl₄ as achlorinating agent for metal oxides but also the catalysis of othermetal chlorides than SiCl₄, to increase the reactivity of those othermetal chlorides as metal oxide chlorinating agents. TiCl₄ is one otherexample thereof, but other metal chlorides catalyzed in reactivity byBCl₃ as metal oxide chlorinating agents, would also clearly fall withinthe scope of the instant invention.

By definition, an ore is a mineral from which the metal values can beprofitably extracted. The term ore as used herein is intended to includerefined as well as raw or native minerals and oxides. Because of thepresent process, metal values can now be recovered economically frommany ores heretofore commercially unattractive because of their highsiliceous content and/or because of the lack of a method to make wastemetal chlorides like SiCl₄ usable as an effective chlorinating agent forthe metal values in useful ores. A current striking need involves themore attractive chlorination of various aluminous ores including clays,bauxites and others previously listed herein, for the production ofalumina, aluminum chloride and aluminum metal. Hence, this uniqueinvention not only profitably utilizes a previously detrimental wasteby-product but simultaneously opens up the economic extraction of metalvalues from many deposits that could not be gainfully exploited withoutthe instant invention.

Incidental Advantages

The apparatus required for the reaction of BCl₃ -catalyzed SiCl₄ with ametal oxide would serve still another purpose. Any carbon monoxide andchlorine evolved from an incomplete reaction in the priorcarbo-chlorination step would react with metal oxide in the apparatus inwhich the catalyzed SiCl₄ was reacted, thus better utilizing reductant,reducing or eliminating costs of recycling corrosive chlorine, furtherimproving the yield of alumina and reducing the volume of gas flow aftercondensation of AlCl₃ and thus lessening of overall process costs.Appropriate amounts of chlorine or of reductant could be introduced intothe second step to cause a balance between them for best utilization ofboth reagents.

What is claimed is:
 1. A process of producing aluminum chloride,titanium chloride, and iron chloride from a calcined aluminous orecontaining aluminum oxide, titanium oxide, and iron oxide comprisingsubjecting the calcined aluminous ore to a decomposition reaction withsilicon tetrachloride at a temperature of from about 500° C. to about1000° C. in the presence of boron trichloride or a boron compound thatwill form boron trichloride in the reaction in an amount of from 0.01 to0.4 on a weight ratio to the silicon tetrachloride wherein a reductantis not used, thereby to produce aluminum chloride, titanium chloride,and iron chloride.
 2. The process of claim 1 wherein the calcinedaluminous ore is calcined kaolinitic clay.
 3. The process of claim 1wherein the calcined aluminous ore is calcined bauxite.
 4. The processof claim 1 wherein the calcined aluminous ore is calcined ferruginousbauxite.
 5. The process of claim 1 wherein the calcined aluminous ore iscalcined siliceous bauxite.
 6. The process of claim 1 wherein thesilicon tetrachloride used is a component of the offgases resulting fromthe carbo-chlorination of an aluminous and siliceous ore.
 7. The processof claim 6 wherein calcined kaolinitic clay is the source of thealuminous and siliceous ore for carbo-chlorination and for thechlorination with silicon tetrachloride and boron trichloride or theboron compound that will form boron trichloride in the reaction.
 8. Theprocess of claim 7 wherein the weight ratio of the boron trichloride tosilicon tetrachloride is about from 0.03 to 0.20, and the temperature ofthe double decomposition reaction is about from 850° C. to 950° C. 9.The process of claim 8 wherein the chlorination is carried out at anabsolute pressure of about from 10 to 200 pounds per square inch. 10.The process of claim 6 wherein the offgases containing silicontetrachloride also contain boron trichloride in a concentration of aboutfrom 0.2 to 12% by weight.
 11. The process of claim 1 wherein thesilicon tetrachloride is a component of the offgases resulting from thecarbo-chlorination of calcined kaolinitic clay using sulfur or afunctionally equivalent catalyst and the aluminous ore reacting with theboron trichloride-catalyzed silicon tetrachloride is calcined kaoliniticclay.
 12. The process of claim 1 wherein the silicon tetrachloride is acomponent of the offgases resulting from the carbo-chlorination ofcalcined kaolinitic clay using sulfur or a functionally equivalentcatalyst and the aluminous ore reacting with the borontrichloride-catalyzed silicon tetrachloride is calcined bauxite.
 13. Theprocess of claim 1 wherein the silicon tetrachloride is a component ofthe offgases resulting from the carbo-chlorination of calcinedkaolinitic clay using sulfur or a functionally equivalent catalystand/or boron trichloride or a functionally equivalent catalyst, and thealuminous ore reacting with the boron trichloride-catalyzedsilicon-tetrachloride is calcined bauxite or calcined kaolinitic clay.14. The process of claim 1 wherein the silicon tetrachloride is acomponent of the offgases resulting from the carbo-chlorination ofcalcined siliceous bauxite using sulfur or a functionally equivalentcatalyst, and the aluminous ore reacting with the borontrichloride-catalyzed silicon tetrachloride is calcined bauxite.
 15. Theprocess of claim 1 wherein the silicon tetrachloride is generated in apreliminary step by carbo-chlorination of calcined aluminous-siliceousore.
 16. The process of claim 15 wherein the calcined aluminous ore iscalcined kaolinitic clay.
 17. The process of claim 15 wherein thecalcined aluminous ore is calcined bauxite.
 18. The process of claim 15wherein the calcined aluminous-siliceous ore is calcined kaoliniticclay.
 19. The process of claim 15 wherein the boron trichloride isintroduced in the carbo-chlorination step.
 20. The process of claim 15wherein the boron trichloride catalyst is introduced into the reactionbetween the aluminous ore and the silicon tetrachloride.